1. Field of the Invention
The present invention relates to an electrode system embedded in an electrically insulating material which in various configurations may be added to existing medical devices such as catheters, prosthetic joints and treatment pads. The present invention combats infections associated with long term use of medical devices.
2. Discussion of the Prior Art
Certain medical treatments require placement of a medical device in a patient""s body. These medical devices sometime provide a path for infection by microorganisms which can contaminate the devices. Such contamination may occur, for example, when the devices are inserted through the skin. The microorganisms, bacteria, and the like tend to migrate along the external or internal surfaces of the devices and thereby give rise to infections. Likewise, other medical devices such as prosthetic joints and treatment pads require long-term placement in a patient""s body and may lead to infections.
For example, bacterial infections of indwelling vascular catheters can be a source of morbidity and even mortality in patients. Such infections are estimated to occur in three to five percent of patients with central venous catheters. Catheter related bacteremia can add 7 to 14 days of hospitalization time and costs, and is often associated with death in these occurrences. To reduce the chances of such infection, surgical placement of tunneled central venous catheters is often done; however, this procedure dramatically raises the costs of catheterization.
Increasing amounts of data indicate that low amperage electric currents are bactericidal, and catheters employing such currents have shown dramatic resistance to bacterial colonization in the laboratory. In that regard, a number of electrophoresis catheters have been suggested. One such catheter applies small DC electric currents between an electrically conductive catheter and an adjacent electrode. Unfortunately, an optimal current density tends to exist only within a small volume of tissue around the point of entrance of the catheter into a patient""s body. Consequently, any microorganisms surviving beyond this small protected volume are free to migrate down the catheter.
Progress has also been made by the use of two parallel, helical electrodes on the exterior surface of a catheter, together with two parallel electrodes on the interior surface of the catheter. This system is described in U.S. Pat. No. 5,324,275, issued to Raad et al. The two external electrodes are partially embedded within the outer surface of a central portion of the catheter tube or lumen, and the two internal electrodes are partially embedded within the internal surface of a hub portion of the catheter. The proximal end of the catheter tube terminates in the hub. Energizing the two separate pairs of electrodes in the presence of a body fluid provides an oligodynamic activity.
Still another catheter design calls for a pair of electrodes to extend along the interior of a catheter lumen and to terminate at the distal orifice of the lumen. The electrodes may be embedded in the wall of the catheter and thereby insulated. They may also be uninsulated, in which case they may be embedded or imprinted along the interior wall of the catheter so as to be kept separate from one another.
It is of interest that previous electrophoresis-type medical devices do not suggest barring or restraining contact between an electrode and body tissues. Primary concerns are for separation of the electrodes from one another, and exposure of at least a portion of the electrodes to fluids present within or around a medical device.
It has now been found that while electrophoresis-type medical devices are effective in reducing infections, they unfortunately can cause other damage to surrounding tissues. In particular, contacts between the electrodes and the tissues can result in serious burns. This is especially the case when the current flow is increased to increase bactericidal action.
The present invention addresses the above problems by means of an electrode system, wherein the surfaces of the inserted medical device contain recessed grooves for receiving one or more pairs of electrodes. The recesses are such that the electrodes are kept out of contact with surrounding tissues, but the recessed grooves are also such that the electrodes are kept separate from one another while being exposed to the tissues. Energizing the electrodes thereby generates an electrophoresis effect and protects the tissues, without burning the tissues.
The present invention provides an electrode system embedded in electrically insulated material used with a medical device which is inserted into an animal or human body. The medical device is in contact with biological fluid and biological tissue and is formed in part of an electrically insulating material. Electrodes are placed into grooves on the body of the medical device so as to enable the electrodes to contact the biological fluid without contacting the surrounding biological tissue. Alternatively, the electrodes may be mounted on the medical device or only partially recessed in the body of the medical device and covered with a fine mesh which allows contact between the electrodes and biological fluid while preventing contact between the electrodes and biological tissue.
One embodiment of the present invention is a catheter which is resistant to microbial colonization. The catheter has an electrically insulated, tissue compatible tube. The exterior surface of the tube contains two or more grooves each of which holds an electrode. The electrodes and grooves are dimensioned as to allow biological fluid to contact the electrodes, while not allowing biological tissue to contact the electrodes. The catheter may also have grooves on the interior surface of the tube. As with the exterior grooves, the interior grooves and electrodes are dimensioned to allow fluid to contact the electrodes, while not allowing solid objects placed into the tube to contact the electrodes. The grooves may be straight and longitudinal relative to the catheter tube or may be helical.
Another embodiment of the present invention is an adapter that can be mated to a standard catheter that is not equipped with electrodes. The adapter is made of an electrically insulating material and may have grooves and electrodes on the exterior and/or interior surfaces. The adapter may be inserted into the standard catheter or may be inserted as a sleeve over the standard catheter. When mated to the standard catheter, the adapter can add electrophoretic anti-microbial protection to the standard catheter.
Another embodiment of the present invention is an iontophoretic treatment pad resistant to microbial colonization. The treatment pad has an electrically insulating, tissue compatible contact surface for contacting the tissue to be treated. The contact surface contains at least two grooves, each groove holding an electrode and being dimensioned as to allow biological fluid to contact said electrode in use without contact between soft biological tissue and said electrode.